This invention relates to maintaining a reliable link.
Mobile nodes include devices such as laptop and portable computers, personal digital assistants, telephones, and other wireless or personal devices may be capable of connecting to a network from varied locations. To connect to an Internet Protocol (IP) based network, for example, a mobile node just needs to be attached to a network to establish a network presence that allows information to be sent between the mobile node and arbitrary points in the IP network.
Referring to FIG. 1, for example, a mobile node 100 can wirelessly and continuously be connected to a network infrastructure 102 using the same IP address regardless of the mobile node's physical location. The mobile node 100 is identified by a home address associated with the mobile node's home network 104. When the mobile node 100 connects to the network infrastructure 102 away from its home link 106, the mobile node 100 is identified by the home address and by at least one care-of address providing information about the mobile node's current location.
Information sent across the network infrastructure 102 to the mobile node's home address is transparently routed to the mobile node's care-of address. The information destined for the mobile node's home address is received at the home link 106 by a home gateway or router 108 that tunnels the information to the mobile node's care-of address via an IP tunnel 110. The care-of address may be an address for a foreign gateway or router 112 that forwards the information to the mobile node 100 over a foreign link 114 that may or may not use IP routing.
As the mobile node 100 changes its physical location and switches to a different foreign gateway or router to maintain connectivity to the network infrastructure 102, the mobile node 100 updates the home gateway or router 108 with its new care-of address. In this way, the mobile node 100 can relocate, connect to various foreign gateways or routers, and maintain a constant IP address presence without interruptions or disturbances in network connectivity. In switching between foreign gateways or routers, however, information may be lost in transit from the mobile node 100 to the home network 104.